The state’s highest court ruled Friday for the first time that police can legally enter private property without a search warrant to rescue endangered animals, a decision that extends the same authority long used by police to save the lives of people.

“The question is one of first impression for this court,’’ Supreme Judicial Court Justice Barbara Lenk wrote for the unanimous court. “In agreement with a number of courts in other jurisdictions that have considered the issue, we conclude that, in appropriate circumstances, animals, like humans, should be afforded the protection of the emergency aid exception.’

The SJC ruling was hailed as a reason for celebration by animal advocacy groups, but generated a warning from the defendant’s attorney that the ruling was so vaguely worded that police can claim concern about an ant farm or a goldfish to bypass privacy rights.

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“If you have an officer who is particularly sensitive to animal injuries, an officer can use this opinion that broad way,’’ said Travis J. Jacobs, a Boston attorney. “I bring up that ant farm and goldfish examples to show the extremes. But lots of times, cases are resolved by extremes. [The SJC] didn’t classify any types of animals that would qualify. The ruling doesn’t limit it to domesticated animals.’’

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Jacobs represents Heather M. Duncan, a Lynn woman being prosecuted for three counts of animal cruelty after police found two dead dogs and an emaciated dog, all still chained, in the backyard of Duncan’s residence on Jan. 8, 2011.

According to court records, a neighbor noticed the situation and contacted Lynn police who first tried to get Duncan’s attention by sounding their siren, ringing doorbells, calling out over their loudspeaker, and through telephone calls.

With no response, Lynn firefighters were called to open a padlocked fence, clearing the way for police to rescue the last surviving dog. When Essex District Attorney Jonathan W. Blodgett’s office tried to prosecute Duncan for animal cruelty, a district court judge ruled that police had no right to enter Duncan’s property, but asked the SJC to review the decision.

In the SJC ruling, Lenk wrote that Massachusetts has a large number of civil and criminal laws on the books that are aimed at protecting animals from being harmed by humans.

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“In light of the public policy in favor of minimizing animal suffering in a wide variety of contexts, permitting warrantless searches to protect nonhuman animal life fits coherently within the existing emergency aid exception,’’ she wrote.

She cautioned that not every circumstance where animals appear to face threats will justify police bypassing legal protections against government intrusion onto private property guaranteed by both the state and federal constitutions.

The SJC had been asked by Attorney General Martha Coakley, the state’s other district attorneys, and the Massachusetts Chiefs of Police Association to reach the conclusion it did, officials said Friday.

Wayne Sampson, executive director of the police chiefs and a former chief himself, said law enforcement has had a duty to protect both humans and animals, and the SJC ruling enhances the ability of police to do that.

Sampson said once inside, if an officer sees evidence of illegal activity, they can refocus their attention onto the new information. But, he said, police are not going to be able to use this new protection for threatened animals as a back door way to get inside the homes of people under investigation.

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“The intent of the officer has to be to go and rescue the animals,’’ Sampson said in a telephone interview. “The court has made it very clear there has to be some reasonable evidence that the dog was actually in physical danger. We can’t just walk in. That’s not what they are saying.’’

In a statement, Blodgett applauded the decision. “This ruling makes clear that police may respond to an emergency in which an animal requires immediate protection or is in imminent danger of physical harm while still respecting the boundaries of the Fourth Amendment against unreasonable search and seizures,’’ he said.

Animal protection organizations including the American Humane Society, the American Society for the Prevention of Cruelty to Animals and the Animal Rescue League of Boston also urged the SJC to reject the defense view of the law.

The court has made it “crystal clear that the same urgency that’s necessary for first responders for people in distress can be applied to animals in distress,’’ said Martha Smith-Blackmore, vice present of animal welfare for the Animal Rescue League. “This is a day of celebration.’’

In a telephone interview, Cheryl Rudolph, president of the Animal Control Officers of Massachusetts, said her members will no longer have to engage in the time-consuming effort to obtain a search warrant as an animal’s life hangs in the balance.

“This is big for us,’’ said Rudolph.“There are times you just need to go in there and get the animal. Now we can respond and do what’s needed right away.”